AP CSC Unit 2

object-oriented programming language (organized in terms of objects)

A value that combines data and the code operating on that data into a single unit (specific instances of classes with defined attributes)

You write a class

A classification that defines a new data type that formally implements (the blueprint) the attributes and behaviors of the objects of that class

classes define new data types that are like blueprints

The properties or what each object knows about itself

What each object can do

The method name followed by the param list that gives the name and type for each param. E.g. - public void inviteFriend ():

Happens when you try to call an object method on an object variable with a null value. Usually means the oject was created without the new operator followed by the class name and ().

A static method is one that doesn’t need to be called on an object of a class. Object methods need to be called on an object of a class.

The dot operator (.), the object, method name, and ending parenthesis. Eg. - yertle.forward()

Allows a programmer to use a method by knowing generally what it does. Like how you can drive a car without knowing how the breaks work

Data you can run into an object’s method

Methods within each class used to initialize attributes in a newly created object (they have the same name as the class)

Use the keyword “new” followed by the class name (Eg. new World()). When it runs, it will create a new object (instance) of that class and call a constructor that has the same name of the class (Eg. new World() creates and initializes a new object of the World class).

A constructor that doesn’t take any passed in values.

When there is more than one constructor defined in a class (E.g. World world1 = new World(); which calls it with default parameters, and World world2 = new World(width, height);). The parameter lists must differ in either number, order, or type of parameters to overload.

Cause an error (not the type of data expected, E.g. turtle parameters must always go x, y ,world)

It says a variable has not been assigned a reference yet (no object to go find in memory). While Turtle t1 = new Turtle(20,20, world); declares that t1 is a turtle instance in Turtle, Turtle t1 = null; or Turtle t1; says that no value has been assigned yet.

A constructor’s name and list of parameters. Can be used to overload a constructor.

Things that allow values to be passed to the constructor to initialize the newly created object’s attributes

Formal parameters are in the constructor’s signature, while actual parameters are values passed into the constructor.

When you pass a value to a constructor or method it passes a copy of the value

Nothing; the point of calling it is to have an effect (do things)

They return a value the code carrying the method call can use; the value returned tells us about the object’s internal state (produce values)

A method that accesses a value in an object, takes no arguments, and has a non-void return type (almost always starts with get, like getWidth)

It returns the value output from the method, and must match the declared return type of the method. The calling method then uses that value.

The parent class of a class (For the String class, its in the java.lang package). Every class knows its parent class (superclass)

You concatenate them with a string object (“String” + nowAString + “String”)

Within quotations, \” prints a quote, \\ prints a backslash, and \n prints a new line

A number associated with a string’s position. It begins at 0. One less than the length of a string (length starts at 1)

the number of characters in a string

a new string that is a part of another string with 0 to all characters copied from the original string

doesn't change index the position of a character in a string

Returns the position of one string in another or -1

Returns a number to indicate if one string is less than (-difference), equal to (0), or greater than another (positive difference) (draw a greater or less than to find out)

Returns true if the characters are the same, false otherwise

Returns a string representing the object that is passed to this method

Returns true if the characters in two strings are the same

0.0-0.99.

(int)(Math.random()*range) + min

max number - min number + 1